diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/CharacterNativeGenerator.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/CharacterNativeGenerator.java
new file mode 100644
index 000000000..bb17ca6ae
--- /dev/null
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/CharacterNativeGenerator.java
@@ -0,0 +1,52 @@
+/*
+ *  Copyright 2014 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.classlib.java.lang;
+
+import java.io.IOException;
+import org.teavm.codegen.SourceWriter;
+import org.teavm.javascript.ni.Generator;
+import org.teavm.javascript.ni.GeneratorContext;
+import org.teavm.model.MethodReference;
+import org.teavm.model.ValueType;
+
+/**
+ *
+ * @author Alexey Andreev
+ */
+public class CharacterNativeGenerator implements Generator {
+    @Override
+    public void generate(GeneratorContext context, SourceWriter writer, MethodReference methodRef) throws IOException {
+        switch (methodRef.getName()) {
+            case "toLowerCase":
+                if (methodRef.getDescriptor().parameterType(0) == ValueType.CHARACTER) {
+                    generateToLowerCase(context, writer);
+                } else {
+                    generateToLowerCaseInt(context, writer);
+                }
+                break;
+        }
+    }
+
+    private void generateToLowerCase(GeneratorContext context, SourceWriter writer) throws IOException{
+        writer.append("return String.fromCharCode(").append(context.getParameterName(1))
+                .append(").toLowerCase().charCodeAt(0)|0;").softNewLine();
+    }
+
+    private void generateToLowerCaseInt(GeneratorContext context, SourceWriter writer) throws IOException{
+        writer.append("return String.fromCharCode(").append(context.getParameterName(1))
+                .append(").toLowerCase().charCodeAt(0);").softNewLine();
+    }
+}
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TBoolean.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TBoolean.java
new file mode 100644
index 000000000..967644e7e
--- /dev/null
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TBoolean.java
@@ -0,0 +1,101 @@
+/*
+ *  Copyright 2014 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.classlib.java.lang;
+
+import org.teavm.classlib.java.io.TSerializable;
+import org.teavm.javascript.ni.GeneratedBy;
+import org.teavm.javascript.ni.Rename;
+
+/**
+ *
+ * @author Alexey Andreev
+ */
+public class TBoolean extends TObject implements TSerializable, TComparable<TBoolean> {
+    public static final TBoolean TRUE = new TBoolean(true);
+    public static final TBoolean FALSE = new TBoolean(false);
+    public static final Class<Boolean> TYPE = boolean.class;
+    private boolean value;
+
+    public TBoolean(boolean value) {
+        this.value = value;
+    }
+
+    public TBoolean(TString value) {
+        this.value = parseBoolean(value);
+    }
+
+    @Override
+    public int compareTo(TBoolean other) {
+        return compare(value, other.value);
+    }
+
+    public static int compare(boolean x, boolean y) {
+        if (x) {
+            if (!y) {
+                return 1;
+            }
+        } else {
+            if (y) {
+                return -1;
+            }
+        }
+        return 0;
+    }
+
+    public static boolean parseBoolean(TString s) {
+        return s != null && s.toLowerCase().equals("true");
+    }
+
+    public boolean booleanValue() {
+        return value;
+    }
+
+    public static TBoolean valueOf(boolean value) {
+        return value ? TRUE : FALSE;
+    }
+
+    public static TBoolean valueOf(TString value) {
+        return valueOf(parseBoolean(value));
+    }
+
+    public static TString toString(boolean value) {
+        return value ? TString.wrap("true") : TString.wrap("false");
+    }
+
+    @Override
+    @Rename("toString")
+    public TString toString0() {
+        return toString(value);
+    }
+
+    @Override
+    @GeneratedBy(ObjectNativeGenerator.class)
+    public int hashCode() {
+        return value ? 1231 : 1237;
+    }
+
+    @Override
+    public boolean equals(TObject obj) {
+        if (this == obj) {
+            return true;
+        }
+        return obj instanceof TBoolean && ((TBoolean)obj).value == value;
+    }
+
+    public boolean getBoolean(TString key) {
+        return valueOf(TSystem.getProperty(key)).booleanValue();
+    }
+}
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TCharacter.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TCharacter.java
new file mode 100644
index 000000000..551e4b8df
--- /dev/null
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TCharacter.java
@@ -0,0 +1,30 @@
+/*
+ *  Copyright 2014 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.classlib.java.lang;
+
+import org.teavm.javascript.ni.GeneratedBy;
+
+/**
+ *
+ * @author Alexey Andreev
+ */
+public class TCharacter {
+    @GeneratedBy(CharacterNativeGenerator.class)
+    public static native char toLowerCase(char ch);
+
+    @GeneratedBy(CharacterNativeGenerator.class)
+    public static native int toLowerCase(int ch);
+}
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
index 3f0514e8d..e1350c903 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TString.java
@@ -72,6 +72,23 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
         this(bytes, 0, bytes.length, charsetName);
     }
 
+    public TString(int[] codePoints, int offset, int count) {
+        characters = new char[count * 2];
+        int charCount = 0;
+        for (int i = 0; i < count; ++i) {
+            int codePoint = codePoints[offset++];
+            if (codePoint >= UTF16Helper.SUPPLEMENTARY_PLANE) {
+                characters[charCount++] = UTF16Helper.highSurrogate(codePoint);
+                characters[charCount++] = UTF16Helper.lowSurrogate(codePoint);
+            } else {
+                characters[charCount++] = (char)codePoint;
+            }
+        }
+        if (charCount < characters.length) {
+            characters = TArrays.copyOf(characters, charCount);
+        }
+    }
+
     private void initWithBytes(byte[] bytes, int offset, int length, Charset charset) {
         TStringBuilder sb = new TStringBuilder(bytes.length * 2);
         this.characters = new char[sb.length()];
@@ -533,4 +550,23 @@ public class TString extends TObject implements TSerializable, TComparable<TStri
 
     @GeneratedBy(StringNativeGenerator.class)
     public static native TString wrap(String str);
+
+    public TString toLowerCase() {
+        if (isEmpty()) {
+            return this;
+        }
+        int[] codePoints = new int[characters.length];
+        int codePointCount = 0;
+        for (int i = 0; i < characters.length; ++i) {
+            if (i == characters.length - 1 || !UTF16Helper.isHighSurrogate(characters[i]) ||
+                    !UTF16Helper.isLowSurrogate(characters[i + 1])) {
+                codePoints[codePointCount++] = TCharacter.toLowerCase(characters[i]);
+            } else {
+                codePoints[codePointCount++] = TCharacter.toLowerCase(UTF16Helper.buildCodePoint(
+                        characters[i], characters[i + 1]));
+                ++i;
+            }
+        }
+        return new TString(codePoints, 0, codePointCount);
+    }
 }
diff --git a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TSystem.java b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TSystem.java
index 7fb6eb876..9b7342956 100644
--- a/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TSystem.java
+++ b/teavm-classlib/src/main/java/org/teavm/classlib/java/lang/TSystem.java
@@ -49,4 +49,9 @@ public final class TSystem extends TObject {
 
     @GeneratedBy(SystemNativeGenerator.class)
     public static native long currentTimeMillis();
+
+    public static TString getProperty(@SuppressWarnings("unused") TString key) {
+        // TODO: make implementation
+        return null;
+    }
 }
diff --git a/teavm-classlib/src/test/java/org/teavm/classlib/java/lang/BooleanTest.java b/teavm-classlib/src/test/java/org/teavm/classlib/java/lang/BooleanTest.java
new file mode 100644
index 000000000..6d1014364
--- /dev/null
+++ b/teavm-classlib/src/test/java/org/teavm/classlib/java/lang/BooleanTest.java
@@ -0,0 +1,32 @@
+/*
+ *  Copyright 2014 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.classlib.java.lang;
+
+import static org.junit.Assert.*;
+import org.junit.Test;
+
+/**
+ *
+ * @author Alexey Andreev
+ */
+public class BooleanTest {
+    @Test
+    public void parsesBoolean() {
+        assertEquals(true, new Boolean("TruE"));
+        assertEquals(false, new Boolean("False"));
+        assertEquals(false, new Boolean("True15"));
+    }
+}
diff --git a/teavm-classlib/src/test/java/org/teavm/classlib/java/lang/StringTest.java b/teavm-classlib/src/test/java/org/teavm/classlib/java/lang/StringTest.java
index 1a32e15c7..5f8e7c15d 100644
--- a/teavm-classlib/src/test/java/org/teavm/classlib/java/lang/StringTest.java
+++ b/teavm-classlib/src/test/java/org/teavm/classlib/java/lang/StringTest.java
@@ -270,4 +270,24 @@ public class StringTest {
         assertEquals(-78, bytes[16382]);
         assertEquals(-69, bytes[16383]);
     }
+
+    @Test
+    public void createsStringFromCodePoints() {
+        int[] codePoints = { 97, 98, 969356, 99, 969356, 99, 100 };
+        String str = new String(codePoints, 0, codePoints.length);
+        assertEquals('a', str.charAt(0));
+        assertEquals('b', str.charAt(1));
+        assertEquals(56178, str.charAt(2));
+        assertEquals(56972, str.charAt(3));
+        assertEquals('c', str.charAt(4));
+        assertEquals(56178, str.charAt(5));
+        assertEquals(56972, str.charAt(6));
+        assertEquals('c', str.charAt(7));
+        assertEquals('d', str.charAt(8));
+    }
+
+    @Test
+    public void makesLowerCase() {
+        assertEquals("foo bar", "FoO bAr".toLowerCase());
+    }
 }
diff --git a/teavm-core/src/main/java/org/teavm/model/util/MutableGraphEdge.java b/teavm-core/src/main/java/org/teavm/model/util/MutableGraphEdge.java
new file mode 100644
index 000000000..3c844c43f
--- /dev/null
+++ b/teavm-core/src/main/java/org/teavm/model/util/MutableGraphEdge.java
@@ -0,0 +1,60 @@
+/*
+ *  Copyright 2014 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.model.util;
+
+/**
+ *
+ * @author Alexey Andreev
+ */
+class MutableGraphEdge {
+    MutableGraphEdge back;
+    MutableGraphNode first;
+    MutableGraphNode second;
+
+    public MutableGraphNode getFirst() {
+        return first;
+    }
+
+    public void setFirst(MutableGraphNode first) {
+        back.setSecond(first);
+    }
+
+    public MutableGraphNode getSecond() {
+        return second;
+    }
+
+    public void setSecond(MutableGraphNode second) {
+        if (this.second == second) {
+            return;
+        }
+        this.second.edges.remove(first);
+        first.edges.remove(this.second);
+        if (!second.edges.containsKey(first)) {
+            this.second = second;
+            second.edges.put(first, back);
+            first.edges.put(second, this);
+        } else {
+            this.first = null;
+            this.second = null;
+            back.first = null;
+            back.second = null;
+        }
+    }
+
+    public MutableGraphEdge getBack() {
+        return back;
+    }
+}
diff --git a/teavm-core/src/main/java/org/teavm/model/util/MutableGraphNode.java b/teavm-core/src/main/java/org/teavm/model/util/MutableGraphNode.java
new file mode 100644
index 000000000..87958f352
--- /dev/null
+++ b/teavm-core/src/main/java/org/teavm/model/util/MutableGraphNode.java
@@ -0,0 +1,58 @@
+/*
+ *  Copyright 2014 Alexey Andreev.
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ */
+package org.teavm.model.util;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ *
+ * @author Alexey Andreev
+ */
+class MutableGraphNode {
+    int tag;
+    Map<MutableGraphNode, MutableGraphEdge> edges = new HashMap<>();
+
+    public MutableGraphNode(int tag) {
+        this.tag = tag;
+    }
+
+    public MutableGraphEdge connect(MutableGraphNode other) {
+        MutableGraphEdge edge = edges.get(other);
+        if (edge == null) {
+            edge = new MutableGraphEdge();
+            edge.first = this;
+            edge.second = other;
+            edges.put(other, edge);
+            MutableGraphEdge back = new MutableGraphEdge();
+            back.first = other;
+            back.second = this;
+            back.back = edge;
+            edge.back = back;
+            other.edges.put(this, back);
+        }
+        return edge;
+    }
+
+    public Collection<MutableGraphEdge> getEdges() {
+        return edges.values();
+    }
+
+    public int getTag() {
+        return tag;
+    }
+}
diff --git a/teavm-core/src/main/java/org/teavm/model/util/RegisterAllocator.java b/teavm-core/src/main/java/org/teavm/model/util/RegisterAllocator.java
index 59c54a43e..c991cfeb8 100644
--- a/teavm-core/src/main/java/org/teavm/model/util/RegisterAllocator.java
+++ b/teavm-core/src/main/java/org/teavm/model/util/RegisterAllocator.java
@@ -35,7 +35,8 @@ public class RegisterAllocator {
         liveness.analyze(program);
         Graph interferenceGraph = interferenceBuilder.build(program, method.parameterCount(), liveness);
         DisjointSet congruenceClasses = buildPhiCongruenceClasses(program);
-        removeRedundantCopies(program, phiArgsCopies, interferenceGraph, congruenceClasses);
+        List<MutableGraphNode> classInterferenceGraph = makeMutableGraph(interferenceGraph, congruenceClasses);
+        removeRedundantCopies(program, phiArgsCopies, classInterferenceGraph, congruenceClasses);
         int[] classArray = congruenceClasses.pack(program.variableCount());
         int[] colors = new int[program.variableCount()];
         Arrays.fill(colors, -1);
@@ -57,6 +58,25 @@ public class RegisterAllocator {
         int var;
     }
 
+    private static List<MutableGraphNode> makeMutableGraph(Graph graph, DisjointSet classes) {
+        List<MutableGraphNode> mutableGraph = new ArrayList<>();
+        for (int i = 0; i < graph.size(); ++i) {
+            int cls = classes.find(i);
+            while (cls >= mutableGraph.size()) {
+                mutableGraph.add(new MutableGraphNode(mutableGraph.size()));
+            }
+            MutableGraphNode node = mutableGraph.get(cls);
+            for (int j : graph.outgoingEdges(i)) {
+                int otherCls = classes.find(j);
+                while (otherCls >= mutableGraph.size()) {
+                    mutableGraph.add(new MutableGraphNode(mutableGraph.size()));
+                }
+                node.connect(mutableGraph.get(otherCls));
+            }
+        }
+        return mutableGraph;
+    }
+
     private List<PhiArgumentCopy> insertPhiArgumentsCopies(Program program) {
         List<PhiArgumentCopy> copies = new ArrayList<>();
         for (int i = 0; i < program.basicBlockCount(); ++i) {
@@ -108,24 +128,34 @@ public class RegisterAllocator {
         return copies;
     }
 
-    private void removeRedundantCopies(Program program, List<PhiArgumentCopy> copies, Graph inteferenceGraph,
-            DisjointSet congruenceClasses) {
+    private void removeRedundantCopies(Program program, List<PhiArgumentCopy> copies,
+            List<MutableGraphNode> interferenceGraph, DisjointSet congruenceClasses) {
         for (PhiArgumentCopy copy : copies) {
             boolean interfere = false;
-            for (int neighbour : inteferenceGraph.outgoingEdges(copy.original)) {
-                if (neighbour == copy.var || neighbour == copy.original) {
+            int varClass = congruenceClasses.find(copy.var);
+            int origClass = congruenceClasses.find(copy.original);
+            for (MutableGraphEdge edge : interferenceGraph.get(copy.original).getEdges()) {
+                if (edge.getFirst() == edge.getSecond()) {
                     continue;
                 }
-                if (congruenceClasses.find(neighbour) == congruenceClasses.find(copy.var) ||
-                        congruenceClasses.find(neighbour) == congruenceClasses.find(copy.original)) {
+                int neighbour = congruenceClasses.find(edge.getSecond().getTag());
+                if (neighbour == varClass || neighbour == origClass) {
                     interfere = true;
                     break;
                 }
             }
             if (!interfere) {
-                congruenceClasses.union(copy.var, copy.original);
+                int newClass = congruenceClasses.union(varClass, origClass);
                 copy.block.getInstructions().set(copy.index, new EmptyInstruction());
                 copy.incoming.setValue(program.variableAt(copy.original));
+                for (MutableGraphEdge edge : interferenceGraph.get(varClass).getEdges()
+                        .toArray(new MutableGraphEdge[0])) {
+                    edge.setFirst(interferenceGraph.get(newClass));
+                }
+                for (MutableGraphEdge edge : interferenceGraph.get(origClass).getEdges()
+                        .toArray(new MutableGraphEdge[0])) {
+                    edge.setFirst(interferenceGraph.get(newClass));
+                }
             }
         }
     }